1. Field of the Invention
This invention relates to the group transfer polymerization of acrylates catalyzed by selected zeolites.
2. Background
Processes are known for polymerizing acrylic monomers to a "living" polymer in the presence of an initiator, which is a tetracoordinate organosilicon compound having at least one initiating site, and a catalyst. Such polymerization processes have become known in the art as Group Transfer Polymerization, (GTP), as disclosed by Webster et al., J. Am. Chem. Soc., 105; 5706 (1983) and also for example by U.S. Pat. Nos. 4,417,034 and 4,508,880. Catalysts known to be useful in such polymerization reactions include a source of bifluoride ions HF.sub.2.sup.-, a source of fluoride, cyanide or azide ions, or a source of certain oxyanions, or a suitable Lewis acid, for example, zinc chloride, bromide or iodide, boron trifluoride and an alkyl aluminum oxide or an alkyl aluminum chloride. Also certain mercury compounds such as mercuric iodide are useful catalysts for the polymerization of acrylates as taught for example in U.S. Pat. No. 4,732,955 issued Mar. 22, 1988 to I. B. Dicker.
An object of this invention is to provide additional catalysts which can be used for the polymerization of acrylate esters using GTP processes disclosed in the aforesaid patents. Another object is to provide such catalysts which avoid the environmental problems associated with mercury compounds; also catalysts which are effective for polymerizations at or above room temperature, which can provide polymers having a narrow molecular weight distribution, and which can avoid a bimodal molecular weight distribution. These and other objects will be apparent from the disclosure which follows.